Illuminated panel



May 5, 1964 A. scHRoPP ILLUMINATED PANEL 5 Sheets-Sheet 2 Filed June l, 1959 INVENTOR, Affzfed Scf MGM" 5, 19641 A. scHRoPP ILLUMINATED PANEL 3 Sheets-Sheet 5 Fille@ June l, 1959;

Il lll//l l ///f////1////////// f /I y?. 39 wm? United States Patent O 3,131,496 ILLUMNATED PANEL Alfred Schropp, 265 Schleissheimerstrasse, Munich 13, Germany, assigner of one-half to Annemarie Grub, Schrobenhausen, Upper Bavaria, Germany Filed .inne 1, 1959, Ser. No. 817,417

Claims priority, application Germany May 31, 1958 12 Claims. (Cl. t0-139) This invention relates to display boards, and more particularly to luminous display boards in which information is conveyed by differences in luminosity and/ or color between adjacent portions of a board.

Luminous display boards are employed for purposes of instruction, of publicity, and generally, for conveying information in a manner readily apprehended by the eye of a viewer.

The signs which convey the information may be luminous dots which may, for example, represent localities on a map displayed. They may be luminous lines, either fully drawn, dotted, broken, in single or multiple color, which may represent lines of traiiic and connections between localities on a map. They may also represent on a chart variations in the magnitude of a value with time, and otherwise convey information or" a pictorial nature or even abstract thought when they form parts of written or printed characters.

It is desired also to present on such display boards differently colored areas juxtaposed in the manner of transparencies so as to distinguish between adjacent areas of a map representing different geographical units or the like.

The luminous displays of the type described are frequently required to be readily formed, deleted, and Vchanged by unskilled persons without the use of special tools or equipment. It is particularly desired that changes be made in a portion only of the information conveyed by the display board while retaining other portions of the recorded information.

This is of particular importance where one portion of the information conveyed by the display remains constant, such as the basic features of a map, whereas variable information, such as temporary location of movable objects or persons is indicated by signs which must be readily insertable, removable, and changeable. When the information conveyed by a luminous display board is of a confidential nature, while it is necessary that the display board be maintained in a location commonly accessible at least at times, it is desirable that information contained on the luminous board be made invisible or unintelligible except at stated periods so that the information need not be removed from the display board during the period during which the board is accessible to persons from whom the confidential information is to be withheld.

It is, therefore, a primary object of the present invention to provide a luminous display board having readily insertable, removable, and changeable signs.

It is another object of the invention to provide such a board the information of which can be altered even by unskilled personnel without the use of special tools or implements.

A further object is the provision of a board which is usable for a substantially indefinite period and on which a substantially unlimited number of pieces of information may be recorded successively.

Still another object is the provision of a display board of the aforedescribed type on which some information may be stored iixedly and protected against accidental removal when other information is deleted from the display board.

Yet another object is the provision of a display board the information on which is available only at a controlled time while being stored on the display board at all times.

An additional object is the provision of such a display board which is of unlimited life, of simple and rugged construction, and not subject to hidden breakdown in which individual pieces of information may disappear unnoticed frorn the board.

A display board capable of simultaneously achieving the various objects enumerated above has heretofore not been available. According to a known arrangement, individual luminous points on a chart, map, or other background on a display board are provided by built-in conducting layers which engage needle contacts of electrical light bulbs used to indicate the points. Such an arrangement is limited in the number of light bulbs which can be supplied by given conductors without thermal or electrical overloading. The life time of the individual electric bulbs is limited and failure of each bulb removes a piece of infomation from the display without warning and without any ready means for detection. This may lead to serious errors.

Maps having luminous points for indicating localities, and luminous lines to represent other features have been presented on display boards by edge-lighted transparent plates in the surfaces of which depressions were formed by drilling to represent localities, and lines for representing other pictorial features and lettering by engraving, localized Sandblasting, and similar operations which permanently destroy the smooth surfaces of the boards. Such edge-lighted plates with signs formed by depressed face portions are practically unalterable and their information cannot even be supplemented by unskilled persons without the use of special equipment.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following detailed description of preferred embodiments of the invention asillustrated in the accompanying drawing in which:

FIG. l is a sectional View of a sign carrier of the invention;

FIG. 2 illustrates an embodiment of the invention having several sign carriers, the view being in section;

FIG. 3 is a diagram representing the switching sequence of the light sources of the device of FIG. 2;

FIG. 4 is a fragmentary, somewhat diagrammatic front elevational view of the device of FIG. 2;

FIG. 5 is a sectional View of a modified light source for use with the devices of FIGS. l and 2;

FIG. 6 shows a switch arrangement for the light sources of the devices of FIGS. 2 and 2 in plan view;

FIG. 7 is a sectional view of another embodiment of a sign carrier ofthe invention;

FIG. 8 yshows a modification of the apparatus of FIG. 7 in side-elevational section; and

FIG. 9 illustrates an ladditional embodiment of the invention lwhich combines features of the devices of FIGS. 2 and 8.

Referring now to the drawing and more particularly to FIG. l, there is shown a transparent sign carrier plate 1 of an optical grade of polymethyl methacrylate. A tubular electric light bulb 3 is arranged along an edge face 2 of the plate 1, the axis of the tubular bulb being parallel to the edge face 2. The plate 1 has a frontal major face 5 and a rearward major face 6 connected by the edge face. All faces of the plate 1 are polished smooth so that light transmitted by the light bulb 3 passes through the edge face into the interior of the plate 1 and is totally reected from the smooth faces where they are in contact with the air. To prevent the escape of light from the plate l at the edge face 4 remote from the bulb 3, the far edge 4 and the other edge portions not adjacent the bulb 3 and not shown in FIG. 1 are coated with an opaque rellecting layer, for example, a coating of White tape, an aluminum foil, or the like, from which light rays are reflected toward the interior of the sign carrier plate 1.

Portions of the major faces S, 6 of the plate 1 are coated with sign layers. The sign layers may consist of any material which alters the totally rellecting properties of the carrier plate 1 by replacing air in Contact with one of the major faces 5, 6. Illustrated examples of such sign layers includes a coating 35 of a transparent or translucent paint on a water, oil, synthetic resin or varnish base which may also include coloring and luminescent matter when applied to the frontal face of the carrier plate 1 will prevent total reflection of light from the coated face portion and will transmit the light outward as indicated by arrows. In a similar manner, a preferably opaque and luminescent paint coating 36 on the rearward face 6 of the carrier plate 1 will dilfract a portion of the light which is being reected from the rear face 5 so that it can pass the frontal face S in an outward direction. It will be understood that the paints have to be adapted to the material of the carrier plate so as to adhere to it, but not to react chemically with the plate in such a manner as to damage the latter. They must also be capable of being removed from the plate 1 by means which will not mar or damage the plate if such removal is contemplated.

Many other materials may be used as sign layers and may be mounted on the carrier plate 1 in a variety of ways. For example, there are shown in FlG. 1 two plastic bodies 7 of different shape which are attached to the frontal face S of the plate 1 by means of pressure sensitive or liquidactuated adhesives. The plastic bodies 7 are transparent and may be colored in any desired manner. They may be produced by any one of the many well-known operations employed in forming plastics.

If light is directed through the frontal face 5 of the carrier plate 1 by an opaque coating 36 on the rearward face 6, it may be modified by a transparent coating 8 on the corresponding portion of the frontal face. Such a transparent layer may be applied by spraying from a gun and will preferably be very thin.

An opaque coating 9 may be placed on the frontal face 5 to appear as a dark spot, lettering, or the like against an illuminated background provided by a coating 1G on the rearward face of the plate 1. The coating 10 itself may consist of letters printed on a transparent backing sheet and pasted on the carrier plate 1 with the letters interposed between the face 6 and the transparent backing sheet, or alternatively, the backing sheet is pasted on the rearward face 6 and the lettering or other signs are applied to the free surface of the backing sheet as shown at 11. A mirror image of what is intended to be viewed must be applied to the backing sheet in this instance.

Additional contrast effects may be achieved by partially adhering a backing sheet 12 to the rearward face 6 of the carrier plate 1. A photograph, drawing or the like on the backing sheet 12 is visible through the carrier plate 1, but those portions thereof which are adhered to the rearward face 6 by means of pressure sensitive or moisture activated adhesives will appear very much brighter as compared to those portions of the backing sheet which are separated from the rearward face d by a layer of air.

Signs may be allixed to the frontal face 5 of the carrier plate 1 by means other than adhesives. A hook 13, a transparent receptacle 14 and a platform 1S are illustrated in HG. l. Objects displayed thereby receive light from suitable coatings on the carrier plate 1 which may provide a contrasting background.

A plurality of sign carrier plates 1 of the type shown in FIG. 1 may be superimposed to achieve multiple effects including those of animation as shown in FlG. 2 in which four carrier plates 1 which are partially superimposed are equipped each with two tubular light sources 16 and 25, 17 and 21, 13 and 212, and 19 and 25 respectively.V The lamps 16 to 19 produce light of one color, say White, whereas the lamps 2d to 23 produce light of a different color, say red. Aside from their function of edge-lighting the several carrier plates of the luminous display board, some of the light sources simultaneously serve other purposes. The lamps 17 and 21 also illuminate a transparency 24.

Each of the carrier plates 1 which are separated from each other by layers of air is provided with sign layers of the type discussed above in connection with the device illustrated in FIG. 1 and capable of diverting light emanating from the respective source of edge lighting through a major face of the respective plate toward the right, as viewed in FG. 2. To a viewer looking at the display board from that direction the several secondary light sources constituted by the sign layers appear to be located in a single plane so that many optical illusions can be produced. Consecutive lighting of sign layers on the several carrier plates may produce the appearance of color changes, of movement, and the like. A combination of a plurality of edge-lighted carrier plates of the invention may also be employed where a large area is to be strongly illuminated in a uniform manner.

Three backing layers 2S, 26, and 27 applied to three respective superimposed carrier plates in offset edge-toedge alignment pro-duce the effect of one large illuminated Iarea when simultaneously and uniformly lighted by the light sources of the three carrier plates. By sequentially lighting the layers 25, 26, .and 27 in a single or `in several colors a great variety of effects can easily be achieved.

The illusion of movement is readily produced by Super- -imposing a plurality of carrier plates as shown at 29. A sign layer a is provided on the carrier plate 1 farthest removed drorn the viewer land is permanently illuminated by the lamps 16, 20. The superimposed second, third, and founth carrier plates have `successive dot sign layers b, c, and d which are in offset edge-to-edge alignment. They are followed, :froml .top to bottom, .as viewed in FIG. 2, by offset sign layens a to d', and a" to d". Some ofthe sign layers are mounted on the frontal faces and sorne on the rearward faces of the respective carrier plates, but both methods of attaching the sign layers may produce the 4same eiect as explained above in more detail.

When the lamps 16 to 19 are sequentially lit in the manner diagrammatically indicated in FIG. 3, three whi-te dots a will appear to travel along a line 60 from a permanent :bright spot at the top .toward the bottom. If the red lamps 20 to 23 .are simultaneously switched on in the sequence 23, 2.2, 21, 20, Ithree red dots will travel countercurnent to the Iwhite dots.

Similarly, a target pattern with widening or narrowing circles can be produced by apply-ing circular line signs 31a to 31d, and 31211 to 32d which are concentric and increase in diameter from a to d on the four superimposed carrier plates. [The effects to be produced by sequentially energizing ,the lamps of the several carrier plates are obvious from FIG. 4 which Iillustrates the target pattern 33 and dn which all circles are simultaneously shown.

Color and other elfeots in the Iluminous display boards of the invention can be produced by lthe edge lighting device shown in FIG. 5 :in ya section perpendicular to the axis of the tubular light bulb 42. The bulb 42 is surrounded by an opaque reeoting layer 43 except for an axial-ly extended slot 44 which transmits light toward the edge of a carrier plate 45 equipped with sign layers and other devices of Vthe type shown in FIGS. 1 and 2. A cylinder 34 is rotatably mounted on the bulb 42 outside the layer y43. It has a plurality of circumferential sec` tions 37, 38, 39, 40, 41, and 46 which differ in their light transmitting properties. The section 37 is completely opaque and the section 46 fully transparent, whereas the sections 38, 39, 40 4and 41 transmit light of selected colorsY only.

To Yproduce .the illusion of 4animation in the apparatus shown lin FIG. 2, each lamp 16 to 23 is equipped with the lighting device illustrated in FIG. 5 and the several cylinders 34 are rotated by hand for automatically by means of -a motor to align the sectors thereof with the slot 44d in la predetermined sequence. Other effects can be produced by making the sectors of the cylinder 34 of helical shape so that consecutive portions of the plate edge simultaneously receive light of different color or intensity. `FIG. 6 shows a blinker switch arrangement for use with the light sources of the luminous sign boards of this invention, and particularly for use with low voltage tinorescent lamps which are the preferred light source. The usual xtures for such lamps have Kfour terminals of which one is directly connected to one pole of the current source, and the second one tothe other pole of the current source by Way of a ballast. The third and yfourth terminal 47 and 48 which are normally connected to Va starter, are respectively connected toa spring mounted movable contact 53 and a Ifixed contact S4. A resistance heating wire 49 forms a shun-t from one contact to the other. It is Wound about .a resilient bi-metal strip 50 'which is longitudinally compressed into ya shallow S shape between two fixed abutments 51 and 52. Because of its shape, the strip S tends to deform transversely in an almost instantaneous snapaction when heated, .and to return similarly to the shape shown in FIG. 6 upon cooling.

This device operates as follows:

When the current is switched on, the wire 49 heats the bi-metal strip 50 which then snaps into the deformed position in which it urges the movable contact 53 against the-xed contact 54 and closes a heati-ng circuit of low resistance through lthe filaments of the iiuorescent bulb, by-passing the resistance wire 49. Cooling of the resistance wire 49 causes the oi-metal strip 50 to `snap back into the yillustrated position after a brief period, thereby opening the contacts 53, 54 and applying the potential drop across the resistor wire 49 to the two tilaments of the iiuorescent lamp for gas discharge. As the resi-stance wire 49 lagain heats the Ibi-metal strip Sti, the contacts 53 and 54 are closed and the gas discharge is extinguished.

This sequence of opera-tions is repeated over and over again, so that Ithe dev-ice described labove constitutes an effective blinker arrangement for uorescent tubes. The same .bi-metal strip may be employed to alternately light and extinguish gas discharge in two Iiiuorescent tubes a-s shown in FIG. 6. The starter terminals .of the second fluorescent tube are respectively connected to a spring loaded movable contact S :and a iixed contact 56 which are closed `when the contacts 53, 54 `are open, and vice versa. Obviously, the device can readily be modified to open and close the contact pairs 53, 54 and 55, 56 simultaneously.

If only a single fluorescent lamp is to be controlled by the blinker arrangement, the device shown in FIG. 6 may be simplified by mounting the contact 53 directly on the bri-metal strip 5t), and connecting bot-h the terminal 47 land one end of the resistance wire 49 to one of the iixed abutments 49 or 5t). If operating conditions are such that the contact S3 needs to be replaced relatively frequently, the more elaborate arrangement shown in FG. 6 ispreferred even if only one iiuorescent lamp is to be controlled.

Another embodiment of the display board of the invention is shown in FIG. 7 in fragmentary side-elevational section. The laminated front wall of the display board is formed by a pierceable board S7 mounted on a resilient backing layer 58 and having a fixed or replaceable facing sheet 59 mounted thereon. The facing sheet may be a map or the like printed or otherwise reproduced on paper. The resilient backing layer is self healing, that is, it tends to close openings formed therein by piercing with an instrument after the piercing instrument is withdrawn. A pointed sign rod 6G and a partially colored sign rod 61 having a rounded end have been inserted into the sign board in such a manner that they pass through the facing 59, the board 57 and the resilient backing 58 and their ends respectively project above the facing 59 and into a light chamber 62 within the sign board which contains several lamps 63. The light chamber 62 is divided into several compartments by a partition 64 which extends between the backing layer 58 and an opaque back wall 69. A sign rod 65 is shown to be partially inserted in the laminated front wall.

When the corresponding lamp 63 is lit, the transparent or translucent rods 60 and 61 appear on the map 59 as illuminated dots. The appearance of these dots is different because of the difference in diameter, the different shape of the ends facing the lamp 63, and because of the coloring of the rod 61. It is also apparent that the cross sectional shape of the rods may be varied to represent a wide variety of data on a map or other facing sheet 59.

As long as the lamp 63 is not lit, the rod 65 is practically indistinguishable from the rods 60, 61. The information stored in the display board of the invention can be kept secret from unauthorized persons by applying a confusing multitude of blind rods which will not, however, interfere with proper interpretation of the data as soon as the lamps 63 are energized.

A modification of the apparatus illustrated in FIG, 7 is shown in FIG. 8. The modified device permits storing several sets of data relating to the same map or chart for simultaneous or sequential viewing. It includes a plurality of superimposed and substantially coextensive light chambers 71, 72, 73 which are separated from each other and from the viewer by laminated walls similar in function and construction to the laminated front wall shown in FIG. 7. The several types of laminated wall construction shown in FIG. 8 are interchangeable with each other and with the frontal wall illustrated in FIG. 7, but each type of wall construction has specific features and advantages not entirely shared by the others.

As viewed in FIG. 8, the visible front of the apparatus faces toward the right. The laminated front Wall is composed of two thin spaced layers of pierccable material 66, 67 between which a layer 68 of self-healing material is sandwiched. Foamed elastomeric material is suitable for this layer. A facing 59 is adhered to the outer layer 66. A lighting chamber 71 separates the front wall from a second wall formed of two outer layers 66, 67 of pierceable material between which several strata of resilient selfhealing material 69 are sandwiched.

The third wall which is separated from the second wall by the lighting chamber 72 and separates another lighting chamber 73 therefrom is of a construction similar to that of the second wall, but the central stratum of resilient selfhealing material has been replaced by a layer 7@ of corrugated cardboard which imparts desirable mechanical properties to the wall.

Sign rods of various lengths, shapes, and light transmitting properties cooperate with the arrangement of a plurality of independently illuminated light chambers and interposed Walls. When the rods are entirely of transparent or translucent material as shown at 7 4, they transmit light from every light chamber which they enter to their free end on the map 59. Depending on the length of the rod, the light is taken from the rst, the first and the second, and from all three light chambers. If desired the rods may be differentiated from each other by providing them with colored portions as shown in rod 61 in FlG. 7.

lf it is desired that a rod draw light only from selected light chambers while not drawing light, or drawing differently colored light from other chambers through which it passes, the respective rod sections are provided with opaque or colored coatings. Blind rods may be produced in a similar manner. Only a few of the possible applications of this basic principle are illustrated in FIG. 8, wherein the rod 7S projects into the first chamber only, and has an opaque coating on the portion thereof which projects into the chamber so that rod '75 is blind Rod 76 passes through all three light chambers, but its portion 81 in chamber 71 is masked olf by an opaque coating. It draws light, therefore, from the second and third chamber.

The rod 77 extends through all cells, but has an opaque coating on the portion 82 in the second chamber so that it will not light up on the map 59 unless the first or third chamber is lit. The rods 78, 79, and 80 extend respectively into the first, second, and third chamber, and draw light exclusively from those chambers since the rods 79 and Sil are provided with opaque coatings 83 in the first chamber, and 84 in the first and second chambers respectively.

It is evident that the sequential lighting method described in more detail in connection with the embodiment illustrated in FIGS. 2 to 4 can be employed to produce the illustion of traveling dots, lines, or other symbols by the apparatus of FIG. 8.

The two groups of embodiments of the invention illustrated respectively in FIGS. l to 4 and 7 to 8 may be cornbined in such a manner that one or several transparent carrier plates with their associated sign layers are arranged in front of a display board of the kind illustrated in FIGS. 7 and 8 so that the map 59 or other facing sheet is visible as a background through the transparent carrier plates, and individual points or other stored information can be made visible in the facing sheet 59 when the light source in a light chamber behind the front Wall is energized. It will be appreciated that the embodiments shown in FIGS. l and 2 may be combined with either the embodiments illustrated in FIG. 7 or that shown in FIG. 8, and that the arrangement of a light source seen in FIG. 5 and the blinker arrangement shown in FIG. 6 are applicable to all these combinations, and to their constituent elements.

An example of a structure combining portions of the embodiments illustrated in FIGS. 2 and 8 is shown in FIG. 9 in which the several elements carry the same reference numerals as the corresponding identical elements in FIGS. 2 and 8. Three transparent sign carrier plates l are superimposed on each other and on the facing sheet S9 of a sign board substantially identical in structure with the apparatus shown in FIG. 8. The plates 1 respectively carry transparent backing layers 25, 26, 26'; and 2'7, 27' which may constitute letters, geographical or other symbols, or pictorial representations. The backing layers, when not illuminated by the lamps 16-18, Ztl-22 are practically invisible. When the lamps are energized, selected backing layers or all backing layers 25-27, 25'- 27' appear as lighted spots superimposed on the map 59.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments or" the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What I claim is:

l. In a luminous display board, in combination, a sign carrier of transparent plate material having a frontal and a rearward major face, said faces being at least partly exposed to ambient air, and an edge face connecting said major faces, at least one of said maior faces being smooth; a source of light arranged to transmit light to said edge face for passage therethrough into said sign carrier and for substantially total internal reflection from said smooth face when the same is in Contact with air; and a sign layer of predetermined shape removably secured in contact with a portion of said smooth face so as to alter the internal reliective properties of said portion and to transmit light falling thereon from said edge face outward through said frontal major face; a background carrier of opaque, yieldably resilient sheet material having two opposite continuous exposed face portions, one of said face portions being arranged opposite said rearward major face and optically shielding a space therefrom; a plurality of sign rods of light transmitting material removably inserted in said background carrier and passing therethrough from one to the other of said face portions, said opaque material being adapted resiliently to close the passages formed therein by insertion of said rods when the same are removed; and a light source in said space for transmitting light from said space through said rods and said sign carrier so as to emanate from said frontal face thereof.

2. In a display board as set forth in claim 1, said frontal major face being smooth, said sign layer being applied to said frontal face and being of light transmitting material.

3. In a display board as set forth in claim l, both major faces being smooth, said sign layer being of light reflecting material and applied to said rearward major face.

4. In a display board as set forth in claim l, a second sign carrier of transparent plate material having a frontal major face spacedly opposite the rearward major face of said first-mentioned sign carrier, a rearward major face and an edge face connecting the major faces of said second sign carrier, at least one of the maior faces thereof being smooth; a source of light arranged to transmit light to the edge face of said second sign carrier for passage therethrough into said second sign carrier and for substantially total internal reflection from the smooth face of said second sign carrier; and a second sign layer of predetermined shape removably secured to a portion ofthe smooth face of said second sign carrier so as to alter the internal reflective properties thereof and transmit light falling thereon from said edge face outward through the frontal major face of said second sign carrier and through said first sign carrier.

5. In a display board as set forth in claim 4, said sources of light respectively transmitting light to the edge faces of said sign carriers being independent of each other.

6. In a display board as set forth in claim l, said sign layer being a body having a face portion mating said smooth major face and adhesively secured thereto.

7. In a display board as set forth in claim 1, a substantially opaque Wall in said space intermediate said sign rods so as to divide said space into two optically separate portions.

8. In a display board as set forth in claim 1, a body of substantially opaque, yieldably resilient material arranged in said space and optically shielding a second space therefrom; another sign rod of light transmitting material removably inserted in said background carrier and in said opaque body and passing therethrough so as to have a rst face portion opposite said rearward major face, a second face portion in said second space, and an intermediate portion in said first-mentioned space; a light source in said second space for transmitting light from said second space through said second sign rod and said sign carrier so as to emanate from said frontal face thereof.

9. In a display board as set forth in claim 8, a coating on said intermediate portion of said other sign rod for preventing passage of at least a portion of the light in said first mentioned space into said other sign rod.

10. In a display board as set forth in claim l, said source of light arranged to transmit light to said edge face being a tubular electric bulb, the axis of the bulb being substantially parallel to said edge face.

l1. In a display board as set forth in claim 10, a tubular body rotatably mounted about said bulb and having a plurality of axially extending portions of different optical characteristics, said tubular body being interposed between said bulb and said edge face.

12. In a display board as set forth in claim 10, blinker switch means for alternately lighting and extinguishing said bulb.

References Cited in the file of this patent (ther references on following page) 2,917,838 Neugass Dec. 22, 1959 8 2,051,288 Curtis Aug 18,1936 g' 2,159,995 Madan May 23, 1939 FOREIGN PATENTS 2,262,930 Gasper Nov. 18, 1941 lo 269,949 Great Britain Aug. 18, 1927 2,347,665 Christensen May 2, 1944 339,115 Italy Apr. 14, 1936 2,476,257 Ho July 12, 1949 579,107 Italy July 8, 1958 2,575,269 H2111 NOV. 13, 1951 626,240 Great Britain July 12, 1949 

1. IN A LUMINOUS DISPLAY BOARD, IN COMBINATION, A SIGN CARRIER OF TRANSPARENT PLATE MATERIAL HAVING A FRONTAL AND A REARWARD MAJOR FACE, SAID FACES BEING AT LEAST PARTLY EXPOSED TO AMBIENT AIR, AND AN EDGE FACE CONNECTING SAID MAJOR FACES, AT LEAST ONE OF SAID MAJOR FACES BEING SMOOTH; A SOURCE OF LIGHT ARRANGED TO TRANSMIT LIGHT TO SAID EDGE FACE FOR PASSAGE THERETHROUGH INTO SAID SIGN CARRIER AND FOR SUBSTANTIALLY TOTAL INTERNAL REFLECTION FROM SAID SMOOTH FACE WHEN THE SAME IS IN CONTACT WITH AIR; AND A SIGN LAYER OF PREDETERMINED SHAPE REMOVABLY SECURED IN CONTACT WITH A PORTION OF SAID SMOOTH FACE SO AS TO ALTER THE INTERNAL RELECTIVE PROPERTIES OF SAID PORTION AND TO TRANSMIT LIGHT FALLING THEREON FROM SAID EDGE FACE OUTWARD THROUGH SAID FRONTAL MAJOR FACE; A BACKGROUND CARRIER OF OPAQUE, YIELDABLY RESILIENT SHEET MATERIAL HAVING TWO OPPOSITE CONTINUOUS EXPOSED FACE PORTIONS, ONE OF SAID FACE PORTIONS BEING ARRANGED OPPOSITE SAID REARWARD MAJOR FACE AND OPTICALLY SHIELDING A SPACE THEREFROM; A PLURALITY OF SIGN RODS OF LIGHT TRANSMITTING MATERIAL REMOVABLY INSERTED IN SAID BACKGROUND CARRIER AND PASSING THERETHROUGH FROM ONE TO THE OTHER OF SAID FACE PORTIONS, SAID OPAQUE MATERIAL BEING ADAPTED RESILIENTLY TO CLOSE THE PASSAGES FORMED THEREIN BY INSERTION OF SAID RODS WHEN THE SAME ARE REMOVED; AND A LIGHT SOURCE IN SAID SPACE FOR TRANSMITTING LIGHT FROM SAID SPACE THROUGH SAID RODS AND SAID SIGN CARRIER SO AS TO EMANATE FROM SAID FRONTAL FACE THEREOF. 